Pages

Follow the reluctant adventures in the life of a Welsh astrophysicist sent around the world for some reason, wherein I photograph potatoes and destroy galaxies in the name of science. And don't forget about my website, www.rhysy.net

Thursday, 28 August 2014

Some considerable time ago, I wrote a short post about much easier life would be if I were a professional pseudoscientist. I happened to mention my favourite "alternative" cosmology - the Space Mirror Mystery. This is the delightful notion that most of what we see in the Universe isn't real but is only a reflection is a huge cosmic mirror (or mirrors). While absolutely ingenious and hugely entertaining, the idea is about as bonkers as it's possible to get.

Much to my surprise, the instigator of this, um, creative idea responded to the post. Well, I couldn't help myself. Most of the website is free, but to access one particular file you have to pay $1001 :

"Hello Pradipta,I see that you offer items for sale on your website. $1001 is quite a lot of money, what do I get for this ? Do you sell actual pieces of the space mirror ?"
The flat-out contradictory response (two months later and you still have to pay $1001) :

"Dear Rhys, There is no price for science. I think you have not understood the theory of space mirror mystery for cause of my bad English. I think if you understand the theory clearly, you may able to making a visual graphic effect and explain the truth to the astronomers. For the welfare of space science the theory needs your help."

No price apart from the $1001 ? Of all the requests for artwork I've had, this is the strangest.

What follows is a choice summary of the "debate" between myself and Pradipta Mohapatra (which you can read in full here) - but first, a short description of this wonderfully bizarre idea. Unfortunately, Pradipta's English is not very good... which makes it all the more entertaining*.

* This is a little cruel, and to be fair, his English is a lot better than my Odia (Oriya). Seriously, if anyone speaks Odia and is willing to help as a translator, get in touch !

From the website, the idea appears to be that the entire Universe is enclosed by a giant mirror about 300 million km wide surrounding the Sun. However, Pradipta assures me that this is not the case, and in a word document (actually just a series of images - bizarrely, since the website is quite well-designed, the text appears to have been typed on a typewriter and scanned in) it appears that there are at least two (possibly four) space mirrors. Are these supposed to be connected, part of a larger, spherical mirror ? I don't know. I assume so, otherwise we'd see nothing at all if we looked out of the plane of the Solar System.

Beyond the mirror there is nothing. Apparently, the commonly accepted distance, size and mass estimates of the Sun are all correct (as presumably are those of the Earth, Mercury and Venus - Mars isn't mentioned) but the giant outer planets have been overestimated. Jupiter, for example, is "really" only twice the size of the Earth (actually it's more like 11) and 153 million km from the Sun, which means at its closest approach to Earth it would be only about 4 million km away ! (actually, it's more like 780 million km from the Sun). But somehow we're being deceived because we're always seeing reflections in that pesky space mirror.

He also states that sunspots aren't real but are somehow caused by the mirror (your guess is as good as mine) and that, just for good measure, there is another Earthlike planet in the Solar System to which there is a "secret root [sic]" we can use to travel between it "and come back safely".

Ooo.... kay....

There are any number of possible ways to disprove this. I do this entirely for entertainment purposes, I am not in the least worried that anyone else might actually believe it (unlike the far more viral, in the literal sense, like Ebola - space vortex video). Some of the more obvious points that come to mind :

1) Dude, are you alright ?
2) If the stars were only reflections in the mirror, which is only twice the size of the Earth's orbit, then the constellations should look distorted as we move toward some (and away from others) throughout the year. They don't (interestingly, Copernicus had the same problem).
3) Those mushrooms look a bit funny.
4) We should see the Sun, Earth, Mercury, Mars, Venus and the Moon reflected in the mirror, but we don't.
5) You've had enough now. Put the bottle back.
6) We've sent spacecraft further away than 300 million km but they didn't hit any "space mirror".
7) I really don't think you're supposed to smoke that...
8) If the mirror encompasses the whole Solar System and nothing exists beyond it, it and everything in the Solar System would eventually heat up and become as hot as the Sun (since there is nowhere for the radiation to go).
9) Whoa, are you sure that stuff is legal ?
10) No explanation is given as to what stars, nebulae and galaxies are reflections of.

I raised some of those points with Pradipta. I never got any clear answers, or any answer at all as to the last point. Admittedly, he did promise answers provided we established the basis of the theory, but amazingly we never got that far. As fas as spacecraft not hitting the mirror goes, he had the following pearl of wisdom to impart :

"Remember that as light the power of remote reflects in mirror. One should keep in mind that targeting on the reflected picture, by a remote device we can get the desired result. Suppose you are watching a space film on a Television set and such film’s image also appears in a mirror opposite. Now you are bored and like to change over through the remote control of the television. You can do so either by directing directly on the television or by directing on image on the mirror.Through remote space organizations have sent man less space vehicle to different space objects like Jupiter, Saturn, Uranus, and Neptune ….etc. Cause of reflections on space mirror those men less space vehicles are going to the real space objects on real root. It may be noted here that since we are able only to see the real space objects situated within the radius of 150 million kilometers from earth and particularly we cannot see anything real space objects out of the above radius of the earth’s darken part, through remote we can never send man less space vehicles out of above distances.”
I think he's trying to say that the transmissions from the spacecraft are reflected off the mirror, which fools us into thinking that they're further away than they "really" are. Except, of course, that this is nonsense - spacecraft point their transmitters toward Earth, not ahead of themselves.

Yes, it's fiction, but it's one of the most accurate pieces of fiction ever.

I also asked exactly how wide the mirror was, but never got an answer. He insists that all of my questions are already answered on his website, but really, they're not. Really really. Honestly, I've spent considerable time looking, but they're not there. Which was why I asked them.

I also tried asking, "why do you think there's a space mirror at all ?" (as opposed to just about all of modern science), which began the discussion in earnest. He answers :

"The theory of space mirror mystery is completely based on a single rule, i.e. “Everything has a limited form or shape”. Can you explain me about any form or shape what have unlimited form or shape? If you unnecessarily try to do so I can easily defeat you by words."
I responded that I didn't understand why everything having a limited shape meant there should be a space mirror, but didn't get any further information about this. However, he continued with what would become the major sticking point for the discussion :

"As the inhabitant of the earth, our astronomers have measured that the size of sun is 3,00,000 times bigger than earth. If sun is 3,00,000 times bigger than earth, then from earth, we must find that an earth like size object would be completely disappeared at the place of sun. Am I wrong ?"
(he's talking here about the mass of the Sun, not its diameter)

"We are living within sun light. So before thinking anything, we should verify how far we could see the space objects within sunlight. It appears from earth, in mass sun is 3,00,000 times bigger than earth, then it also appear to me that an earthlike object would completely disappeared at sun’s distance. Am I wrong? If yes, let me answer at which distance earthlike object would be completely disappeared from earth."
Later, he emphasised this further :

"Unless/until our eyes objects, we are able to see the vast space. Whatever we see through our eyes, telescope enlarges the same. If anything objects our eyes we cannot see beyond that, neither telescope will help us through it.""An object how bigger it may be, become smaller and smaller as it goes away and away from our eye sight, the thing appears us smaller and smaller till it disappears from our eye sight."

So it appears that he doesn't believe it's possible to see things if they're too far away. Well, while that's true as far as it goes (but watch out - we'll get back to this soon) this doesn't actually explain anything. If you can't see something that's too far away, you won't be able to see its reflection either. Specifically, he thinks that objects which appear to be extremely distant are the result of multiple reflections between the two mirrors (or two opposite sides of the same mirror). But this obviously doesn't help, because reflections get progressively smaller too. So if you can't see something 150 million kilometres away, you won't be able to see it if its reflection looks like it's 150 million kilometres away.

He also doesn't explain why we don't see multiple reflections of various objects.

Moreover, why the fact the Sun is big and far away specifically means that an Earth-sized planet would not be visible at the Sun's distance is pretty cryptic (Pradipta is insistent on this point and seems to think it's obvious). Nonetheless, I tried very hard to answer this.

As things get further away, they look smaller. We both agree on this, at least. This basic fact was best explained by the inimitable Father Ted :

The apparent size of an object depends on its true physical size and its distance from the observer. There's nothing very interesting or profound about this, it's just a basic property of perspective. We can quantify the apparent size of an object by its angular size - that is, what fraction of our field of view it takes up. This is geometry at its simplest.

If you were to stand in the center of a football stadium, you'd be able to turn a full 360 degrees and see the stadium all around you. Of course, you'd only have to look up, say, 20-30 degrees before you start looking at the sky. The Sun and the Moon are both about half a degree across, or roughly the size of a penny at arm's length. The smallest thing you can see is about 0.02 degrees... sort of.

More accurately, the smallest thing you can resolve is about 0.02 degrees. All that means is if something is too far away, you can't see it as anything more than a featureless point. For a penny, you'd have to move it about 28 metres away before you couldn't see any structure to it (please do try this at home). But, if it was a bright, sunny day, and the penny was a nice shiny new one, you could still see it glinting in the sunlight, even if it was much further away. It might be too small to resolve, but that doesn't mean it would be so small it would stop reflecting all light back toward you.

And that's the key point. Angular size never reaches zero. But - and this is crucial - Pradipta insists he's not merely talking about anything being too small to see with our eyes :

"I don’t ask you about any large enough telescope, what could detect a planet at any distance....Completely disappear means zero. Neither the object would be visible to earth nor does any telescopic instrument help us to detect through it."He also explicitly asked :

"Then my question is very clear “at which distance would the earth like object be completely disappeared from earth?”
I'd already tried explaining that things never completely disappear no matter how far away they are (that's impossible, as we'll see in a minute) but he didn't accept this. So for the sake of giving an answer, I calculated the distance at which it would become invisible to our eyes.Well, just like moving a penny 28 metres away, if we move an Earth-size planet 43 million kilometres away we'll only see a point of light. As we move it further away, it will appear fainter and fainter. At about 1.3 billion kilometres, it will be as faint as the faintest star we can see with the naked eye. This is a fairly simple calculation - you can check my maths here, if you like that sort of thing. All it requires is the size and luminosity of the Sun, and the size and reflectivity of the Earth (surprisingly, Pradipta accepts the standard values for these).

A very simple sanity check indicates that this answer can't be too wide of the mark. We can certainly see Mercury with our eyes, even though it's much smaller than Earth and can be further away than the Sun is (though it can be pretty close to the visibility limit). Uranus, accepting standard values, is only a few times bigger than Earth, at least 1.6 billion kilometres distant, and just about visible to the naked eye.

But Pradipta was not happy with this answer for several reasons. First, he said it assumed "a constant lightening atmosphere". Of course, it didn't. We know that light decays in proportion to the square of the distance - so if you move twice as far away from the light source, the amount of energy received goes down by a factor of four. That's a critical part of the calculation. And then there was his continuous insistence that things can completely disappear - not merely fall below the resolution of our eyes, but actually reach an angular size of zero if they're far enough away :

"Friend, kindly observes the facts. Our existence has been started from sun and we know the distance between earth to sun is 150 million kilometers. So it is logically proved and clearly appeared if an earthlike object moves from our earth toward sun, would be completely zero at the sun‘s distance. This fact proves also the position of earth always zero everywhere at the distance of 150 million kilometers. So we can never see or detect any illuminated objects of sun beyond 150 million kilometers."

How, exactly, the fact that the Sun is big and far away is clear and logical proof that we wouldn't be able to see an Earth-size planet at that distance is, I'm afraid, something that quite escapes me.

Here's why things never disappear completely, no matter how far away they are. Suppose I'm looking at a large red stick, because why not.

You'll probably want to open the links to see the images full size. I kept the stick and the observer the same screen size, just to be extra clear that what happens really happens and isn't some kind of CGI hocus-pocus.

You'll notice that the observer's lines of sight to the top and bottom of the stick form a triangle, with the stick being the third side. As we move the stick further away, the triangle gets longer and sharper - the angular size of the stick gets smaller and smaller, from 45 degrees at 2.4m distance to just 1 degree at 114.6m. The angle between the observer's two lines of sight is the angular size of the stick.

That's the crux of the matter - no matter how great the distance, we can always draw a triangle using the two lines of sight and the stick, and so the stick always has some angular size. Now it may be an incredibly thin, sharp triangle if the stick was a billion kilometres away, but there isn't some freaky limit beyond which triangles don't exist. The angular size can get arbitrarily small, but it can never, ever reach zero.

So if it's a choice between believing that all of science is wrong, or that triangles exist, I'll choose triangles, thanks.

Pradipta's response ?

"As per your images you have shown about triangles marking as ‘A’ as the viewer point of the observer and ‘B’ ‘C’ are the points of a stick of two meters length. If a match’s stick would be 2 inches length, mathematically you are also getting never ending answer because you are following wrong procedure and drawing the unending lines imaginary and blindly believe that everything can be discovered through telescopic instrument. Of course your mathematic is correct for a limited extend and telescopic instruments may function within such limitation."

Sigh. I posted a counter-response asking what the limit is at which the mathematics breaks down (and what exactly happens to stop triangles existing), but he said that would be his last reply. So I don't think he's coming back. Pity.

You may wonder why I even bothered debating such an outlandish idea. Well, several reasons (besides hilarity). Firstly, it appears that Pradipta genuinely believes his idea and isn't trying to scam anyone (I suspect the $1001 is a typo). Secondly, he was willing to debate in a sensible, polite and courteous manner with no name-calling or personal attacks. But mostly I was curious what pattern of thinking could have lead him to an idea so far removed from reality that it's fallen off the edge of the flat Earth. Interestingly, he thinks his ideas are entirely rational - there's no hint of any underlying religious motivation. And unlike the space vortex author, Pradipta does not have any links to ozone hole skeptics or other dangerous conspiracy theories (as far as I can tell), so the whole thing seems like a harmless enough piece of folly.

I've also been thinking a lot lately about the point at which science dismissing alternative models becomes unscientific and arrogant. I'll explore this in detail in the next post, but for now, I'll note only this : science is built on facts. Interpretation may be subjective, but facts aren't. It is an inherent part of the scientific method that if it disagrees with observation, it is wrong. Sometimes this can be harsh and unpleasant, but it's the only way to make progress.

Finally, Pradipta, if you're reading this, I sincerely thank you for the polite discussion. I think your idea is very clever, but absolutely and unequivocally wrong. I urge you to take some classes in basic mathematics (especially geometry) and astronomy. If you are open to listening to the facts, I think you will soon learn why there is not, and cannot, be a giant space mirror.

EDIT : An Unfortunate Postscript
Some time ago, Pradipta ended the discussion with the rather strange phrase :"Whatever it may be? [no idea what this is referring to] Then you believe: Space mirror = Zero"
Yes ! That's right, I believe space mirror equals zero, i.e. it does not exist ! Tough to see any ambiguity in that statement to my mind. Well, I didn't deign to reply further, it just seemed a waste of time.
A few weeks later, Pradipta decided to send the following email to the astronomy staff at Cardiff University :

"Dear Sir,

I have no doubt about your intelligence.

As an advocate, I plead on behalf of entire world that nothing is real beyond 150 million kilometers except mere reflections. I strongly plead that as the inhabitant of earth and within sun light, we are able to see the real space objects within the radius of 150 million kilometers only. Since we get ourselves as zero at the distance of 150 million kilometers, space mirrors appear us on two points, viz, on the point of earth’s shadow and point of sun.

On above rules, the theory of “SPACE MIRROR MYSTERY” is formed and we claim:

Item No-1 Sun is the only star of the solar system as well as the universe and it can be proved.

Item No-2 The space objects what we have observed within 300 million Kilometers from the sun are real space object and ahead of 300 million Kilometers are mere images of the space objects situated within 225million Kilometers to 300 million Kilometers from the sun. From calculation it appears that the real Jupiter, Saturn, Uranus, Neptune & Pluto are 253, 264, 277, 288 & 292 million Kilometers respectively from sun.

Item No-3 In mass, the real Jupiter is two times bigger than earth but we observe the image Jupiter as twelve times bigger than earth and same real Saturn, Uranus & Neptune are smaller than earth.

Above was strongly objected by Rhys Taylor, Astrophysicist, Astronomical Institute, Prague. I believe he is convinced at zero concepts after a long debate. Please read that debate between me and Rhys in the following link

Note: Please share this to your astronomical colleagues if you appreciate."

Let me state this in terms so clear there can't be any doubt by anyone at all, ever : FUCK OFF PRADIPTA. Your assumption (for the second time) that my lack of response somehow equals my agreement is retarded. Stop it. At no point in any part of the discussion did I remotely entertain the notion of a space mirror; both of these posts couldn't be any frickin' clearer on this point. If you post them to a bunch of academics, it's going to be obvious to them that this is the case. Claiming that they state the exact opposite of what they say is to my mind rather a lot worse than a personal attack. It is is equivalent to claiming that I'm a Moon landing conspiracy theorist or a global warming denier; a line has been crossed beyond which I feel no obligation whatsoever to remain civil. Further discussion can serve no purpose. Any additional comments are subject to deletion entirely at my whim. Goodbye.

Tuesday, 26 August 2014

An epilogue to the press release on the long gas stream, or part 4 in the trilogy if you like. Actually this will form the first part of another trilogy, dealing with alternative ideas and pseudoscience. This one makes for a nice, gentle introduction - in the next post we'll go to far stranger places, where triangles don't exist...

Here is an email I received a few days after the press release. The author (name withheld, referred to only as "k", presumably for dramatic effect) presents, very politely, their ideas regarding galaxy formation. Some of it is not so different from standard theories, but there are a few... (ahem) anomalies.

My commentary on the original text is in square brackets and in blue. Here's the main figure from the press release again, as a reminder of what we're talking about.

Dr. Rhys Taylor.

Dr. Robert Minchikn [sic - but now I'm finding hard to avoid mentally replacing "Minchin" with "Munchkin", or possibly "MinChicken", Robert's not going to like that...], et al, great work.

[Thanks !]

Source of this cloud of gas?

I am reluctant to say [No you're not, you've written a whole book about this, but we'll get to that later] (because no one will believe this). Your discovery supports my contention that all the galaxies associated with these streams of gas were once closely associated, that is, all have a common antecedent or origin. Those streamers point roughly back to that common origination point.

[Well, certainly the stream of gas itself most likely originates with the galaxies in question, and in all probability those galaxies were once close enough to interact and draw out the gas gravitationally (or possibly via ram pressure stripping). So this part seems fine, though the "common origin of galaxies" idea is worrying. The mainstream idea is "hierarchical merging" - lots of small objects form first, then merge - pretty much the exact opposite of this "hierarchical fragmentation", as I guess you'd call it. That's not too outlandish though.

In conventional astronomy, the galaxies are continually moving through space. At some point in the past they happened to move past each other, and during the short time they were close enough, some of their gas got removed. Now they're far apart again.

As I wrote in an interview for Vice.com, an alternative explanation is that the gas in the stream is primordial - that is, left over from the formation of the Universe and condensing along dark matter filaments. This is an extremely controversial idea, and doesn't seem very likely to me (see link for details).]

The original proposition was -

At some stage of universal development early universe filaments segmented into what became, called here, Omega bodies [Oh dear, that sounds like an unfortunate attack of drama. Just call them proto-galaxies or proto-clusters. Dramatic names are a turn-off]. Notable is that these segmented ‘chunks’ were nearly equal in mass size [to each other ?] (check the math) [err, what math ??]. (That process is described very simply here.) [Poor use of brackets and ambiguous statements aren't helping credibility at this stage. If you're smart enough to create a revolutionary theory, you're smart enough to use brackets sensibly, dammit.] Most of these primordial objects had spin and angular momentum, plus other qualities not discussed here.

Some, during their high velocity passage through space, acquired a a sizable volume of dark and other matter. To illustrate this feature see Kappa Cassiopeiae, HD 2905, star bow shock wave,Credit NASA, JPL, Caltech

Measuring many light years across, this ‘baggage’ acted to slow the passage of the Omega body.

[Well, that's perfectly reasonable - acquiring more mass means the shock will slow down due to conservation of momentum.]

Shocks formed by contact passage through varying densities of mostly dark matter were transmitted through the dark matter bubble to the Omega body causing it ultimately to disintegrate. Plus, other processes not described here were instrumental in the breakup of these high density objects.

[All well and good as alternative cosmologies go. Doesn't bear any resemblance whatsoever to conventional ideas, but that's OK, let's run with it. More about this later.]

The constrained matter surrounding the object was instrumental later for the formation of galaxies.

[What prevented them forming stars immediately ?]

(As per the discoveries of Minchin, et al [which ones ?], streamers and batches of gas lost along the way mark the journey’s path of the Omega ‘fragments’ to their ultimate destination.)[If this means, "current" destination, then that's OK. If it literally means the place at which they will reside until the end of time, then it's impossible. In a gravitational field you can never be at rest. Also, we know galaxies are moving through space because we can measure this directly.It's especially important to avoid colourful language when presenting unconventional ideas - I've had emails of various levels of crazy, so I've no way of knowing what sort of idea (genuinely plausible or downright impossible) I'm dealing with from a new contact. Throughout the rest of this post, I'll give the benefit of the doubt and assume the least crazy idea whenever things are ambiguous.]

Those Omega bodies that had little spin loosened their parts more or less omnidirectionally, not very distant. The galaxies that developed from these were later very prone to collide and merge with each other.

[More or less self-consistent, I guess, but let's wait a minute.]

Most of these primordial ‘rocks’ [Benefit of the doubt that this is colourful language again] had high spin rates [Why ? This is important, because the following text makes it clear we're dealing with rotational energies orders of magnitude greater than what we observe in galaxies today]. The first fragments to come off were flung a great distance. Each taking with it a share of the accumulated dark matter. (Dark matter in these cases was like the yolk of an egg.) [Perhaps it was a laid by a MinChicken...] See the chart by Dr. McCall. (To whom I am most grateful. Note that he does not agree with the scenario described here.) 'Council' sheet views, McCall[Original, entirely respectable articlehere][Thing is, objects don't get "flung" a specific distance in a gravitational field in a vacuum. They can only be put on different orbits - or, if they are sent off fast enough, they escape entirely. They can be flung at different velocities, but that's quite different to sending them a set maximum distance due to their initial speed. The point is they won't ever stop - they'll keep moving on curved paths through space.]

The first sibling pieces in our family to come off the progenitor Omega body, each weighing multiple [many hundreds of billions of] solar masses, were M83, M64, NGC 253. [OK, I guess he's saying that the more distant galaxies from us formed first because they seem to trace a ring. In this scenario, a giant spinning cloud flung out galaxies to produce the distribution we see today.]

At the same time many smaller units were launched. Each loss of mass to the Omega body reduced the forces of angular momentum. Until finally we have the last division that gave us our Milky Way and Andromeda [presumably since we seem to be at the center of the ring]. In that manner Omega had sacrificed itself to seed more than a hundred new galaxies. [Is this poetic or was Omega literally sentient ? Again, colourful language doesn't help. There really are people out there crazy enough to believe in giant sentient gas clouds as the origin of the Galaxy.]

It was spin that caused these units to detach along a plane. (The process or morphology of how these ‘bits and pieces’ of mass developed into galaxies is described elsewhere.)

[Actually though, the fact we see smallsatellite galaxies in planes around giant galaxies is really interesting. It wasn't predicted by standard simulations, and there have been claims that this is something modifying our theory of gravity explains better than invoking dark matter. Most people think it's a problem with our lack of understanding of the complicated physical processes at work in the gas (which the simulations don't deal with). I think it's very intriguing, but not yet enough to convince me we should throw out the dark matter model.The dispute in contemporary, mainstream science is not as to whether small galaxies can be formed by larger galaxies tearing off pieces of each other - everyone accepts that - but how common this is. Unfortunately, k is talking notabout small galaxies forming this way, but giant ones (as in the press release that prompted the email, and in McCall's paper). And he's not talking about the galaxies being in a plane because it's easier, gravitationally, to remove gas this way (the mainstream view), but because the Omega thing was spinning really fast. To a normal astronomer this sounds very strange indeed - but does it make any sense ?

Let's start with that that ring of galaxies. The claim appears to be that the galaxies furthest from the center were formed earliest. k strongly implies that he believes galaxies can get flung to certain distances by their initial speed, after which they just sit there. As already mentioned, we know that's not true. For the sake of benefit of the doubt, let's see if we can salvage the claim anyway.Is the ring even real ? Well, here's McCall's image stripped of annotations. Judge for yourself - but remember, McCall was deliberately restricting his analysis to galaxies within a fixed, radial distance. The fact the corners are empty doesn't mean anything, because galaxies there were excluded from the study (to be absolutely clear, McCall wasn't trying to make any of the claims k is; his work is entirely mainstream research).

Even if those dozen-odd galaxies really are distributed in a neat ring, does that really mean anything ? Context may help. Here's the distribution of 11,000 galaxies on a very much larger scale, fifty times that of McCall's selection :

You can certainly see plenty of structures in there, though they're very much larger than in the McCall study. Here's another large-scale schematic, from the Sloan Digital Sky Survey. The scale here is twice as big again as the last one.

That intricate network of filaments, sheets and voids has been reproduced extremely well by standard models - it's one of the great triumphs of modern cosmology (regardless of all its other problems). Even those who dispute the existence of dark matter cannot question its success in reproducing these structures. While, as I mentioned, there are problems producing the correct structures on the scale of a single galaxy, on the scale of giant sheets and filaments, there aren't. Since this result is not at odds with standard theory, it can hardly be used as evidence for an alternative model. At most, all it says is that the alternative model is not ruled out. To have evidence that the alternative is better, you'd have to find a configuration of galaxies that the standard model doesn't predict but the alternative does. That is categorically not the case here.

Furthermore, to me it seems like a heck of an inference to invoke a radically different alternative model based on the distribution of a handful of galaxies... even if they were in a much more obviously weird configuration, like a cube. Small number statistics are at work. That is, if you pick only a dozen of so galaxies at random in a small region, and it would be easy to find a ring-like distribution - particularly if you select galaxies in a spherical volume. The ring distribution, real or not, is therefore completely and utterly meaningless.Further-furthermore, the whole model of some primordial gas cloud spinning apart and sending huge galaxy-size chunks that formed the current distribution seems deeply flawed to me. Spinning a gas cloud is going to cause the entire thing to expand, not rip chunks out of it*. As it expands, it might fragment - but this is complicated. To suggest that this would produce a nice configuration of galaxies wherein we can infer their formation history merely by their distance is fantastically unlikely at best. That's just not how orbital motion (or even, more generally, motion in a vacuum) works - things keep moving.* To be fair, k says that the cloud disintegrates due to shocks with the dark matter and "other processes not described here". Obviously, I can't comment on the other processes. Dark matter halos, however, could not cause a cloud to disintegrate into discrete chunks - they, like the gas clouds, have a smooth distribution. They could distort the cloud due to tidal forces, but not cause it to fragment. Nor could they be responsible for causing the cloud to spin-up (unless it happens to move past two dark matter halos in just the right way) - and if the cloud was previously spinning so fast, it would have broken up beforehand anyway.As you'll have no doubt gathered, I think this whole idea is wrong every which way.Specifically, what goes up, must come down - or escape forever. When something is sent on an orbit that moves it radially outwards, then unless it's going so fast it escapes completely, it eventually falls back again. Interplanetary spacecraft, for example, can be sent on Hohman transfer orbits to reach their destination. This requires not only that they fire their rockets to leave Earth, but also that they fire them again to enter the same orbit as their target planet is moving around the Sun. If they didn't do this, they'd end up falling back to their starting point. The point is they need to exert some force to get themselves into a nice circular orbit. Energy must be expended, you can't just change from an elliptical to circular orbit whenever you feel like it - that's just as bad as saying that things get flung a specific distance. Since the galaxies can neither be static nor thrown into stable circular orbits, I can't see any way to make this work.

DeltaV means the spacecraft must fire its rockets to generate
a change in velocity at these points to follow the green transfer orbit
(deltaV1) and enter the red circular orbit (deltaV2).

(I've been assuming here (for the sake of generosity) that most of Omega's dark matter remains at the center. If it disintegrates along with the galaxies it flings out, things will be even worse - there'll be nothing holding the galaxies in orbit at all, so they'll just fly apart.)But wait ! Galaxies don't have rockets, it's true... but what if they keep detaching parts of themselves as they go ? When you get right down to it, losing mass is what makes rockets go faster (Rocket science ? Easy. Rocket engineering... not so much). The problem is the galaxies would have to preferentially shoot bits of themselves off in only one direction, otherwise, like a Catherine wheel, they're not going anywhere. And if they're shredding themselves by spinning, well, that basically is a Catherine wheel writ large.

OK, so if we can't deduce the formation history of the galaxies just by measuring their distance away from us, could we do something more complicated ? Perhaps the galaxies will preserve their original formation in the pattern of their relative positions ?No. If and when our giant galaxies return to their point of origin... well, you'll have a whole bunch of galaxies crashing together (or at the very least, strongly interacting with one another and the dark matter remaining in the center). That is not going to result in the galaxies moving apart again neatly, to say the least. After that first return, the positions of the galaxies (assuming they even survive, which is unlikely) won't tell you a darn thing about their formation history.]

If you take a volume of space encompassing a radius of 20 to 50 million light years, most likely you will find some discernable structure to the arrangements of galaxies therein. But, not in all areas of this universe. [Which is perfectly consistent with standard cosmology, so can't be taken as evidence for the Omega bodies.] Some of those Omega bodies are still out there just waiting for something to happen (dark galaxies).[Not if they have the mass of a hundred galaxies they're not - we would easily have detected hydrogen masses this large by now. Believe me, I've looked.] A few others exploded; galaxies formed but no structured order was established.

Those that had the right amount of spin, plus other opportunities, much like ours, formed a planar pattern of galaxy formation. The large galaxies, mostly spiral, in turn followed the example of their progenitor by producing satellite galaxies in a similar manner. (That subject is covered thoroughly elsewhere.) [Same problems as before - what makes the galaxy spin up ? Will conditions be right in the expanded gas for fragmentation and star formation ? How can this produce galaxies on the correct orbits ? Too many things...]

The depth or width of the ‘super galactic plane’ is governed by the amount of wobble the Omega body had. In our case there was not much. Increased wobble can cause the Omega fragments to be dispersed over a wider range. The resulting galaxies are arranged in a broader plane.[Self-consistent, I guess. I still don't see how you'd form a staggeringly massive cloud of hydrogen without it forming stars though.]

It can happen that a primordial object has/had a secondary spin axis. This causes its loosened parts to be scattered all around. Galaxies, usually elliptical, form in a random pattern.[Well, that's just not true. The morphology-density is very well-known. Most elliptical galaxies are found in the center of clusters, while most spiral galaxies dominate the population outside clusters.]

This Omega model of sibling galaxy structure is quite simple, even simplistic. Others can do a much better job of explaining it. So much research needs to be done.

[The book description from amazon :]
How do galaxies get started? How do they change and morph from one design to another? Be forewarned – The story as told here departs quite a bit from the accepted view of the nature and behavior of what is called a black hole, and specifically the nucleus of a galaxy.
Conventional science claims that you can only know the mass size or weight of a black hole and its relative spin rate. Stuff can enter a black hole, but nothing can leave. Called a singularity – scientists claim black holes have unique properties; which if explained to you, you would not understand; so don’t ask [??? Yer whaaa.... ????]. A few seem to treat the black hole as some kind of unknowable Quantum Deity. Others think of them as giant macrophages [I had to look that up in a dictionary, it means "white blood cell"] that go around gobbling up waste and useless material, gorging on worn-out stars and used up matter [Nonsense, pure and simple - black holes will consume anything that gets too close, they don't have a preference for "waste matter". That's not a remotely scientific idea]. Taken to the extreme, given enough time black holes will gobble up everything that exists. Then what? Do they go around gulping down each other, until there is just one big black hole left? “That’s all, Folks.” Can that be the ultimate fate of ‘all there is’? Quoting TV’s Judge Judy – “If it doesn’t make sense, it’s not true.” [There are too many things wrong with that. No further comment]. Applying that rule [!], does it make sense that possibly galaxies have a definite birth followed by growth, and eventually give birth to new galaxies?
Cover image credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)
The cover image captures the overlapping galaxies 2MASX J00482185-2507365 in the act of separation. In the scenario described here the larger galaxy has given birth to the smaller. Could instead as claimed by scientists the smaller came from outer space and is approaching the larger? There are ways to tell the difference.

For the daring few of you that are tolerant of contrarian concepts, read on – k[I read the sample available on amazon. Suffice to say the text is erroneous, and, like most pseudoscience, full of terrible English, and more unusually, repeated (use of multiple) (brackets for some reason). Come on, if you must invent dreadful theories, at least learn correct punctuation.]I was initially sympathetic when I read this. In some ways, it's not such a silly idea - the fact that the satellite galaxies of the Milky Way and Andromeda are found in planes is a subject of genuine intense controversy. Indeed, some, though a minority, argue that those structures are best reproduced by interactions, with one galaxy interacting with the other in the same plane. That's close to saying a galaxy got spun-up and smaller ones broke off. Sort of. Maybe. Not really.But the idea that the distribution of a dozen nearby giant galaxies somehow supports this Omega model is simply wrong. The observed distribution of giant galaxies into filaments, sheets, and voids, is very well-reproduced by standard theory. Moreover, predicting which galaxies formed first based on their spatial position doesn't work either, because, as we know, galaxies are continually moving through space. The whole "everything was flung out of something else and has a common origin" idea, as we've seen, just doesn't work at all.I lost patience on reading the book sample. The thing basically amounts to "revisionist science" - taking accepted ideas to mean something completely different, then saying everything else is also wrong to fit his idea. A polite way to put it would be, as Jon von Neumann reportedly said, "With four parameters I can fit an elephant, and with five I can make him wiggle his trunk." If you have enough unknown variables, you can make your model do anything. In this case the author is deciding that some variable are unknown when they're really not... so a less polite version would be, "you're making stuff up."

As we'll see in the concluding part of this trilogy, this has nothing to do with being tolerant of "contrarian" ideas. Science does not permit tolerance of things which are demonstrably wrong - that's what pseudoscience is for. Stay tuned for the next exciting (and much more fun) installment, wherein I disprove the existence of a giant space mirror by means of triangles.

Sunday, 24 August 2014

If you're reading this and thinking, should I buy a "Lego Mindstorms kit ?", let me save you the trouble and say yes. Yes you should. Because it's brilliant. Don't bother reading the rest of the post, because that's all you need to know.

I'm a great believer in self-rewarding for significant achievements. Completing my PhD got me a laptop, now 4 years old and still going strong - the second most expensive thing I've ever purchased, but by far and away the best. Publishing my thesis data got me a large glass brick (full of thesis data), which I use in just about every presentation possible. This time I'm celebrating publication of another data set, one which took an inordinately long time.

Lego Mindstorms has always been a case of, "yeah, looks fun, but I don't think I want to spend £200 on Lego." Fortunately, I had a £100 gift voucher from my friends at Arecibo when I left.
"I'll spend it wisely", I said.
"That's a shame, we were hoping you'd spend it foolishly", they said.
That was obviously a far better idea, so that's what I did.

I am not a hardware person. As a child, Meccano was OK, but I didn't have the patience to screw everything together (though for some reason typing in programs on a ZX Spectrum wasn't a problem). Woodwork was just a bit meh. Sewing was tedium itself. As for electronics, circuit diagrams give me a paroxysm of bewilderment while my soldering was the inspiration for the death scene of the T1000 in Terminator 2.

But even I can put Lego together from a kit. Plus I already know how to code in Python (which you can use to control Mindstorms if you're that way inclined, and I am), and the fact the kit comes with the parts for not one but five different robots sealed the deal for me (actually there are now official guides for fifteen !).

Each robot comes with 5 different "missions" which can involve modifying the robot and/or the code to control it. So far I've completed the missions for the most basic robot, the "Tracker". This is a simple tracked robot that demonstrates just about all the major features. It took me about 1-2 hours to construct.

In the box, you get bags and bags of >500 Lego pieces. Sadly there's no plastic container within the box to hold them all, so, having read another review beforehand, I went out and bought some Tupperware boxes. That was extremely sensible, since the raised rims of the lids stop the pieces from falling off when I'm gathering the requisite parts. The parts in each bag were pretty well organised so I kept them in the same system. It's simple to find whichever part I need.

I don't recommend just throwing all the parts in a big bag unless you want to give yourself massive Lego-rage later. Especially since there are a few parts you only get one of. Seriously, no, don't do it. Those boxes were quite a lot more full before the Tracker was built, and there's more in the shoebox.

Apart from the Lego, the box contains the instructions for the most basic robot (with handy parts guide and a ruler), and the cover of the box detaches to form a mission mat (where you can test some of the specially-designed programs). The full manual and instructions for the other robots are available online, unfortunately there's no printed version. But you're going to need to be on a PC to program the robot anyway, so that's not really an issue*. A nice thing about the online guide is that it gives you full 3D, rotatable views of each step of the build process, which can be incredibly helpful when assembling some of the more fiddly bits.

* I think it is possible to program the Lego directly, but I can't imagine why you'd want to.

Batteries aren't included either, so go out and buy a few packs of AA and AAA batteries (requires 6 AA and 2 AAA). You'll also, annoyingly, need a very small crosshead screwdriver to open one of the battery compartments.

The build quality is what you'd expect from Lego - genius. Unlike the cheaper imitations everything fits together pretty easily, but is robust enough to withstand some persuasion, when needed. Things don't fall apart unless you want them to. Assembling the Tracker was about the closest I've felt to being 10 years old again since Jurassic Park was re-released at the cinema. Sheer delight. In about an hour - a very, very happy hour - I had a little tracked robot roving around the house, servo-motors making pleasant whirring sounds.

Next step, add lasers.

The basic idea of Mindstorms is very simple - you have a programmable brick which can take input from different sensors and control different motors accordingly (the brick itself can light up, show simple images on its quaint LCD screen, and make sounds - "INPUT, STEPHANIE !"). The demo program just makes the robot rotate and move a bit, then stop. Switching it to manual infra-red control was simple and a lot more fun. The robot easily clambers over small obstacles and even quite respectable slopes.
(sometimes the IR stops working and I have to turn the robot off and on again, but I haven't updated the firmware yet)

Things get more interesting with the various missions, which teach you how to program the robot and use the different sensors. Programming is done not by typing out code (that's possible but I haven't tried it yet) but by visually placing different blocks in a sequence. Each block can take input from the sensors (e.g. determine how far away the nearest obstacle is with the infra-red sensor), affect the program itself in some way (e.g., wait for a few seconds, repeat some action), or control a motor.

The instructions on how to create the program blocks were simple, though the interface itself could maybe be a little streamlined. It has a few too many similar buttons that do different things, for example, a + button in one place will start a new project, whereas a + button very close to it will merely start a new program. I'm not really sure what the distinction is for, other than causing confusion when I press the wrong button. However, actually "writing" the programs is very easy indeed - it's an intuitive drag-and-drop interface.

The only difficulty I ran into was enabling the Bluetooth connection to the computer. The programmable block can connect via USB, Bluetooth, or wi-fi (but wi-fi requires a USB dongle, not supplied). Unfortunately the USB slot isn't accessible on the assembled robot, so Bluetooth was the only practical option. It wouldn't have been majorly difficult to take the programmable block out, but it would have been irritating - the cables that connect the sensors and motors to the block are long and inflexible, making things a bit awkward.

Anyway, I found the secret was to enable Bluetooth on the block (duh), but not to use the blocks "connections" setting to find the PC. Instead, use the Mindstorms software on the PC to connect to the block. That seemed to do the trick. So now I can press a button on my PC and a little robot will start shooting plastic balls at some miniature rubber tyres. Which is immensely satisfying.

EDIT : After updating the firmware, the only way I can connect via Bluetooth is to make a connection via the Lego brick itself, then turn it off, then connect using the PC software. That's quite annoying as it takes 1-2 minutes to do this. On many (most) designs, disconnecting the brick would be very difficult or even impossible without disassembling the entire robot.

Things got more interesting with the other Tracker missions. The basic model has a spinning blade, while others have a bazooka (shoots plastic balls a few feet), a gripper (very cool, my favourite - robots with hands are just innately more awesome) and a hammer (classic Robot Wars). My favourite mission was with the hammer - the program makes the robot jerk around like it's developed an unfortunate disorder, hammer twitching spasmodically, until you sneak up on it from behind. Then it turns around and gives you a good thump. Wonderful.

All of these accessories connect interchangeably to the "medium motor" (the large motors are used to drive the caterpillar tracks) and demonstrate ingenious ways that rotational motion can be used to do cool things.

As you can see, a rather nice feature is that there are enough parts to build all the accessories separately - you don't have to take apart the bazooka to build the gripper. Sure, it could use a few more spares, but it's hardly lacking.

With the kit you get a touch sensor, a colour sensor, and an IR detector (which can find the distance to nearby objects). It can also, somehow, sense the direction to the IR controller. You can also buy extra sensors online (the manual even mentions that it's designed for use with third-party sensors), like temperature and ultrasound (a Lego sonogram , anyone ?). The output of the sensors was easy to understand in the program builder - it was trivial to make the robot stop when it detected an obstacle, for instance. You can even control the whole thing from a tablet, though I've yet to try that.

The recommended age for this product is 10+. That's just stupid. If I had a ten year old there's no way I'd share it with them. They won't enjoy it on as many levels as I do.

I'd love to tell you more but I think I desperately need to build the six-legged walking robot now.

Friday, 8 August 2014

Apparently, when scientists talk to the general public they're supposed to sound "excited" and "enthusiastic" about their work. That probably explains why they wouldn't let me write the press release about the latest paper. Here's what I would have written.

Astronomers and students using the Arecibo Telescope have found a bridge of gas 2.6 million light years long between galaxies 500 million light years away. And they seem to be pretty pleased about that, because finding gas is "a jolly good thing", they say, in amusing British accents.

The bridge of gas (shown in green) stretches from the large galaxy at the bottom left to the group of galaxies at the top. A third nearby galaxy to the right also has a shorter stream of gas attached to it. Picture credit: me/Arecibo Galaxy Environment Survey/The Sloan Digital Sky Survey Collaboration, http://www.sdss.org

Admittedly, the stream of gas is probably the largest known, a million light years longer than a gas tail found in the Virgo Cluster by another Arecibo project a few years ago. So that seems to make it fairly interesting. Gesticulating wildly, Dr. Rhys Taylor, a researcher at the Czech Academy of Sciences and lead author of the paper, allegedly made a bold, melodramatic statement that, “This was totally unexpected. We frequently see gas streams in galaxy clusters, where there are lots of galaxies close together, but to find something this long, and not in a cluster, is unprecedented.”He then briefly passed out from the sheer excitement of it all.While such allegations remain unsubstantiated, what he definitely said was, "This is a pretty hefty stream of gas. OK, it's really long, but that's no reason to take seven bloody months to referee the paper. I suppose it's kind of neat, maybe even exciting a year ago, but all of that has been ground out of me by the extremely tedious peer review process. Hell, seven months is only slightly shorter than a pregnancy. I think I need a nice cup of tea, or possibly a nice cup of whiskey."Other researchers on the project remain more upbeat, probably because they didn't face a series of "badly-worded" and "downright strange" concerns to address from the referee. Roberto Rodriguez, a recent graduate from UPR Humacao, was so enthusiastic he worked on AGES data for two REU programs and two research-for-credit modules, and basically just wouldn't quit. "He even shows up now he's graduated," says project leader Robert Minchin, "which is great because now we have a willing vict- volunteer who does the work of a postdoc without any of the cynical ranting or the pesky need to provide funding and travel support."Roberto enthusiastically explained, “We normally find gas inside galaxies, but here more than half of the gas – over 15 billion times the mass of the Sun – is in the bridge. That’s far more than in the Milky Way and Andromeda galaxies combined ! Also, on an unrelated note, Rhys totally bakes the best brownies ever. Have you seen his website ? I am saying this entirely of my own volition.”The team doesn't have any convincing explanations for how the stream formed though. "Errr...." said Rhys, looking gormless, "Maybe one galaxy pulled the gas out of the other... because... umm... gravity ? Or maybe it just pushed all the gas out of the way. I dunno. What am I, a magician ?"Sensibly, the team plan to use computer simulations to try and understand how the bridge formed. They haven't got very far yet, because all of their attempts to even form a stable gas disc have blown up in their faces - literally. "I just don't understand it," said Rhys, despondently, "It just sits there for about 400 million years happily enough and then it explodes for no reason. On the other hand, we've only been at this for three days, so give a guy a break."

The project involved three undergraduate students in the research work. As well as Roridguez, the team included Clarissa Vazquez, now a graduate student somewhere in America-land, and Hanna Herbst, now also a graduate student at the University of Florida. Dr. Robert Minchin, a staff astronomer at Arecibo Observatory, principal investigator on the project, professional beard-wearer and undisputed air hockey champion of Green Bank 2011, said “Student involvement is very important to us. We are proud to be inspiring the next generation of astronomers, and particularly proud of the involvement of Puerto Rican students, because they are the shizzle.”Rhys adds, "Damn straight. I don't understand why Roberto is still here. If someone doesn't snap him up for graduate school, there's something very wrong with the system. But at least we get to keep him for a while longer."

STOP PRESS : With just hours to go before publication was due, Roberto announced that he had indeed been accepted into graduate school, and there was much rejoicing. The bridge, as well as a whole bunch of other fairly interesting things, was found in data taken between 2008 and 2011 for the Arecibo Galaxy Environment Survey (AGES), which is using the awesome power of the Arecibo Telescope to survey a large area of sky with a high level of sensitivity. After a long-winded review by other, hopefully cleverer astronomers, the discovery has been accepted for publication in Monthly Notices of the Royal Astronomical Society. A pre-print of the paper can be found at http://www.arxiv.org/abs/1407.0016.The Arecibo Observatory is operated by someone under a tremendously complicated and boring legal agreement with some other people.

Wednesday, 6 August 2014

Now that the bitter cynical ranting is over, it's time for a much more positive note about the research I've been doing for the past year or so. You can, of course, now read the full, magisterial* paper online, if you want the gory** details.

* Read, "fairly interesting".** Read, "dull".
This is the second part of the trilogy of posts relating to my latest paper. The first was about the peer-review process that is the backbone of modern science, the third (coming soon) will be about what we discovered. In this one, I'll explain a bit about how we detect galaxies, without which we wouldn't be able to do anything at all. Specifically, this is going to be a very pragmatic post about how we look at the data and find what's in it; if you're more interested in how we get the data, you should wait for the third installment. What I'm going to describe here amounts to just three paragraphs in the paper, which should hopefully give you some idea of the work involved in a publication.

For the purposes of this post, the one-line summary is that we point our radio telescope at the sky, tell it to look for hydrogen, and then make maps of the hydrogen over a small part of the sky. We can measure not only how bright the emission is and where it is, but also what frequency (or velocity) it's emitting at. So we don't just get a normal 2D map to look at - we get a 3D data cube to search. And that's not easy.

You Could Probably Train A Monkey To Do This, But Not A Computer

In fact, finding hydrogen is very boring. It is. It really, really is. That's because although our data is three-dimensional, there are very few good programs* to let us view it in 3D. Consequently our poor students have to spend weeks looking at things like this :

* The redoubtable ds9 is one, but its features are limited. VisIt is an alternative, but it's so feature-packed it comes with a 30 page "quick" start guide (surely an oxymoron) and I can't get it to do anything.

What you're looking at is our data converted into a series of 2D slices. Each bright blob is a hydrogen detection (we'll get to why they look like that in a moment). What's even worse than having to view it in this unnatural, uninteresting way, is that there's no way to mark the detections when you've found them. You just have to try and remember which one's you've found. And with a particularly galaxy-rich data set like this one, that's simply impossible.

That didn't stop my student from doing an absolutely freakin' awesome job of cataloguing them, but it did take her about six weeks to find them all.

Now you may be wondering, why not just write a program to detect the hydrogen automatically ? Wouldn't that be faster and better ? In fact, no - in this case computers are, for once, slower and worse. The reason is that humans have had millions of years of evolution which give us pattern recognition skills that are, frankly, frickin' awesome. I mean, c'mon, look at this :

... or this...

... or this...

Now, even though I didn't tell you what to look for, you almost certainly spotted the lion and the tiger essentially instantly. Did you spot the velociraptor before reading the caption ? Don't answer, that was a rhetorical question. The point is, even without any instructions, you can identify threats in what are (compared to hydrogen data cubes) incredibly complex scenes with sufficient speed that you could decide to run away, if necessary.

Puerile though the joke may be, the last scene is actually a very good, nay, excellent analogy for hydrogen detections. The velociraptor is quite hard to distinguish from the foliage, just as hydrogen sources can be very faint. Also, the scene is dominated by a young lady afflicted by back problems, who is far more obvious than the raptor. In real data, artificial radio sources from satellites, radar, wi-fi, mobile phones etc. etc. etc., are often much brighter than the galaxies we're trying to detect.

Which is why one night a group of enterprising REU students decided to remove the road signs advertising mobile phone coverage. I mean, c'mon, they were stuck on the Observatory gate, for heaven's sake. I woke up to find one lying outside my front door.

It's obvious to a human observer that the velociraptor is much more threatening than our meditating friend - not so for a computer. You might be able to write a program to detect danger by looking for, say, nasty big pointy teeth, but asking it to be able to classify any possible animal and make a threat assessment is really rather a tall order. Similarly, it's not too difficult to write a program that finds hydrogen, but it's a lot harder to write one that doesn't find a lot of rubbish as well.

There's one other aspect of the meme that makes it extra perfect. Even if you haven't grown up terrified of velociraptors thanks to watching Jurassic Park when you were ten years old, even if you've somehow never heard of a velociraptor (God help you, you don't know what you're missing), you can still identify it as an animal. It just looks like one. Now, since velociraptors are all dead, we could call it a false positive in our search for threats. Similarly, we sometimes find things that look exactly like hydrogen detections, but aren't real. That's why we take extra "follow-up" observations whenever we're unsure.

OK, so our super-smart monkey brains can spot danger really quickly, and don't need anyone to do any astonishingly complicated pattern-recognition programming. Huzzah ! But now imagine that your task was not simply to detect and run away from the predator, but to make a quick sketch of it first (gosh, this is a good metaphor, isn't it ?). That's the crux of the problem - not detecting the hydrogen, but recording it quickly.

"Blender ? That's Your Answer To Everything !"

For some time, I'd been tinkering in my spare time with ways to import astronomical FITS files into 3D modelling/animation software Blender. I knew from the first time I sat down and catalogued a data cube that the software we were using was maddeningly inefficient. You couldn't even copy the coordinates of a detection to a file once you found one - you had to type them out yourself. It was a totally ridiculous waste of time* to spend days or weeks looking at blobs on a screen instead of trying to do actual science. And I knew that if I could only import the data into Blender somehow, all my problems would be solved at a stroke - the tools I needed were already an intrinsic, fundamental part of Blender**.

* A.k.a. "character building", or more accurately, "soul destroying."** That's NOT why I wanted FITS files in Blender though. I just thought it would look cool.

I would not describe myself as a professional programmer and I tend to think of writing code as an option of last resort. Way back at the start of my PhD, I had no idea how to use the Python scripting language that Blender uses. I started learning it as a side-project to import simulation data (which was relatively easy - we'll get to why in a minute) for a friend. That gave me enough Python knowledge to try importing FITS data in various ways. You can read about my earlier efforts here. Initially I was limited to importing only the brightest pixels in the data - crude, but enough to see the data in 3D.

The same data as in the above movie, but now (crudely) rendered in 3D. Right Ascension and Declination are just position on the sky. Almost all the galaxies here aren't well resolved by Arecibo spatially, so they look like blobs on the sky. But they are very well resolved in the third axis (velocity) since they're rotating, so they look like long, cigar-like blobs in 3D. This is much better in .glass format.

The problem is that it's relatively easy to import and display a few thousand or tens of thousands of discrete data points in Blender, but it's very much harder to import a few tens or hundreds of millions of data points that form a continuous volume - like a FITS file. Anything less than that might be OK for making pretty pictures, but wouldn't be "science quality" - for example if the display was limited to showing only the brightest hydrogen, we'd miss the faint stuff, which can be the most interesting. But if you display the weak emission, you generally have to display the noise in the data as well, and that means you need to display huge numbers of data points.

This is what one million dots look like. To do anything useful with astronomical data, we need some way to visualise at least one hundred million data points.

It took another year or so in Arecibo, playing around in my spare time, before I hit upon a more useful solution than displaying a bunch of dots*. Trying to create a million little dots in Blender would be difficult, but it can easily handle an image of one million little dots. So by slicing the data into a series of images and then mapping each image onto a virtual Blender object (a simple flat plane), it would be possible to display the data without having to remove all the faint, potentially very interesting emission.

*Another problem with this methods is that in Blender, the dots can't have any colour information in the realtime view - so very bright sources look the same as very faint ones.

Now, at this point I could cut a long story short, but I'm not going to. Why ? Because it was bloody difficult, that's why ! With still very limited knowledge of Python, I needed a proof-of-concept that this method could work. I used a program called kvis (which we normally use for viewing the data in 2D) to create images of slices of the data. It only outputs in the obscure .ppm format, so then I had to convert them into something Blender can read like .png. Then, as an initial test, I manually loaded a bunch of these images into Blender, using each one to control the transparency of the plane it was mapped on to. This is massively impractical - if your cube has 100 pixels on a side, it needs 100 slices to show everything, and loading each one is boring. But it worked.

Pretty convincing for a bunch on planes.

Now I was really getting somewhere - I could view volumetric data in realtime without needing to cut any of the faint emission. The concept was proven, so I began working on this in earnest in between supervising a summer student, who was usually busy searching the cube the hard way with kvis, and finally publishing the data from my thesis. First, I had to find a workaround for a major problem with Blender : viewing the data from behind. Somehow, what looks great from one angle just looks mwwurrrgh (technical term) from the reverse angle.

Bugger.

After a couple of weeks wrestling with this one, I eventually consulted the Blender forums and found that the workaround was to create a copy of the image planes and put them somewhere else. Making a copy somehow "resorts" the textures so they look fine from the opposite direction. So then I wrote a little script to automatically change which images should be displayed depending on the orientation of the viewpoint. Swivel around too far and it automatically changes the view to that of the image copies instead of the originals.

That made things almost useful. A great deal of struggling with Blender's Python reference eventually allowed me to load the images automatically, which was infinitely more practical than loading them one at a time. The reference guide is, unfortunately, fantastic if you basically know what you're doing but not a great source for tutorials, but after a lot of trial and error I was able to make it work.

"Finally", I also had to teach myself matplotlib to avoid having to use two other programs to convert the data. That was relatively simple since the documentation was much better. This still only gave me the very very basics of what I wanted, but it was working : I could load any FITS cube I damn well wanted and look at it as nature intended, in 3D, with a few mouse clicks.

That wasn't the end though. Looking at it in 3D is nice, but not very useful by itself - the axes of the data need labels ! For that, I had to learn how to convert the pixel values into coordinates, something I'd been perfectly happy to let other programs do by magic. I never wanted to go into the details of world coordinate systems or write a routine to decide where it would be best to place the tick marks. But without this, no-one would ever take it seriously, me included. It would be a cute little gimmick, nothing more. Eventually I figured that one out too.

That meant I could also click on a source and know exactly where it was on the sky. So now instead of manually writing the coordinates down, you just click on a source and Blender calculates the position for you. Even better, you can add an object to hide the source, so that you never forget which sources you'd detected. You can turn the "masks" on and off if they're causing problems. Although you can do all this with other programs, they're not interactive - you have to enter the box coordinates manually and then re-load the data, which is much, muchslower.

The upshot of this is that instead of having to spend weeks tediously poring over a data cube finding galaxies, you can get that stage done in about a day. It's about 50 times faster than using kvis. Conclusion ? Rhys wins. I didn't put that in the paper though.

Epilogue

Fast-forward about a year and the prototype had been developed into an all-singing, all-dancing FITS viewer now called FRELLED. Now it could load files with a user non-hostile interface very reliably. Another year or so and it could load simulations, cross-reference NED and the SDSS, plot contours and automatically create animations to impress people. Tasks that previously took minutes now take seconds, tasks that took weeks now take hours. If I had a TARDIS, I'd go back in time to PhD-me and say, "Rhys ! Forget the data analysis ! Learn Python, you dolt !".

Worryingly, that probably is the first thing I'd do if given access to a time machine.

Currently, after about two years of on-off work, FRELLED is more or less "core complete". It does everything I need it to, plus a few things I need it to do now that I didn't need it to do before. It's also evolved to the point where (I hope) the user really doesn't need to know anything at all about Blender. It's gotten pretty complex, so it still throws a wobbly from time to time when someone does something unexpected, but generally, through much toil, it's pretty stable.

You may be wondering, well, was it worth it ? YES OF COURSE IT WAS YOU STUPID PETTY FOOL ! HOW DARE YOU QUESTION - err, by which I mean, yes definitely, because it's not just useful for the incredibly niche aspect of looking at hydrogen data cubes. That's certainly what it's best at, of course.

But it can do a lot more than that. In principle it can load in any volumetric data set. Here, for example, is an MRI scan of a banana flower that someone converted into a slice-by-slice 2D GIF, which, with a small amount of tweaking, I was able to reconstruct this back into 3D in FRELLED :

Of course, simulations are even more fun because we can watch things evolve with time. Here's one that went wrong because the galaxy melted :

So, FRELLED has made my day-to-day life a lot easier, giving me more time to watch YouTube (don't worry, that's just astronomer-speak for "do ground-breaking science") and consume copious amounts of tea. In the future, it may become even more useful. Current surveys have at most a few thousand hydrogen detections... pretty soon, thanks to newtelescopes and instrumentation, we'll be in the era of hundreds of thousands of detections. Rather than rely on those slow, unreliable programs to detect the hydrogen, with FRELLED (or something like it) and maybe a bit of crowd-sourcing, potentially we could let humans do the pattern recognition they're so good at without eating up years of astronomer's valuable time. I call that a success.